Hong Seok Lee
Chonbuk National University
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Publication
Featured researches published by Hong Seok Lee.
Scientific Reports | 2015
Minh Tan Man; Hong Seok Lee
The influence of the growth conditions of multilayer CdTe/ZnTe quantum dots (QDs) on Si substrate upon their carrier dynamics is studied using intensity integration and broadening photoluminescence. The unusual temperature dependence of the line broadening is explained using a model for interband transitions that involves a lowest discrete electronic state (1Se) with different discrete hole states (1S3/2 and 2S3/2) and a 1P transition. These transitions are expected to play a critical role in both the thermally activated energy and the line broadening of the QDs. We also demonstrate that a thermally activated transition between two different states occurs with band low-temperature quenching, with values separated by 5.8–16 meV. The main nonradiative process is thermal escape assisted by carrier scattering via emission of longitudinal phonons through the hole states at high temperature, with an average energy of 19.3–20.2 meV.
Optics Express | 2012
Hyun Jeong; Yong Hwan Kim; Tae Hoon Seo; Hong Seok Lee; Jun Sung Kim; Eun-Kyung Suh; Mun Seok Jeong
We report on the efficiency enhancement in GaN-based light-emitting diodes (LEDs) using ZnO micro-walls grown by a hydrothermal method. The formation of ZnO micro-walls at the indium tin oxide (ITO) border on the LED structure is explained by the heterogeneous nucleation effect. The light output power of LEDs with ZnO micro-walls operated at 20 mA was found to increase by approximately 30% compared to conventional LEDs. Moreover, the finding of nearly the same current-voltage characteristics of GaN-based LEDs with and without a ZnO micro-wall shows that the ZnO micro-wall does not influence the electrical properties of the device but only leads to an increase in the light extraction efficiency. From the confocal scanning electroluminescence results, we confirm that ZnO micro-walls enhance the light output power via the photon wave-guiding effect.
Journal of Physics D | 2011
Hyun Jeong; Tae Su Oh; Yong-Seok Lee; Hyung Gu Kim; Chang-Hee Hong; Eun-Kyung Suh; Ok Hwan Cha; Hong Seok Lee; Mun Seok Jeong
We investigate the local electroluminescence (EL) characteristics of c-plane blue InGaN/GaN light-emitting diodes (LEDs) with periodically arranged dodecagonal micropits (DMs) which have {1?0??1??1} and {1?1??2??2} facets using confocal scanning electroluminescence microscopy (CSEM). By increasing the injection current from 1 to 20?mA, the EL peak for c-plane LEDs is shifted to a shorter wavelength (by up to 5.5?nm), but the EL peaks for semi-polar {1?0??1??1} and {1?1??2??2} facets are nearly unchanged because of the substantially reduced polarization-related electric fields in the quantum wells. CSEM images show various emitting distributions due to the different emission origins as a function of peak position in the EL spectrum. The present observations can help one to improve the understanding of the spatial origin of increased external quantum efficiency in InGaN LEDs with DM arrays.
Journal of Nanomaterials | 2014
Mun Seok Jeong; Gon Namkoong; Clare Chisu Byeon; Jong Su Kim; Hong Seok Lee
1 Department of Energy Science, Center for Integrated Nanostructure Physics, Institute for Basic Science, Sungkyunkwan University, Suwon 440-746, Republic of Korea 2Department of Electrical and Computer Engineering, Old Dominion University, Norfolk, VA 23529, USA 3 School of Mechanical Engineering, Kyungpook National University, Daegu 702-701, Republic of Korea 4Department of Physics, Yeungnam University, Gyeongsan 712-749, Republic of Korea 5 Department of Physics, Jeju National University, Jeju 690-756, Republic of Korea
Applied Science and Convergence Technology | 2015
Minh Tan Man; Hong Seok Lee
Quantum-confined nanostructures open up additional perspectives in engineering materials with different electronic and optical properties. We have fabricated unique cation-exchanged CdS and CdS/CdSe quantum dots and measured their first four exciton transitions. We demonstrate that the relationship between electronic transitions and charge-carrier distributions is generalized for a broad range of core-shell nanostructures. These nanostructures can be used to further improve the performance in the fields of bio-imaging, light-emitting devices, photovoltaics, and quantum computing.
Nanoscale | 2014
Hyun Jeong; Doo Jae Park; Hong Seok Lee; Yeong Hwan Ko; Jae Su Yu; Sang-Bae Choi; Dong-Seon Lee; Eun-Kyung Suh; Mun Seok Jeong
Journal of Luminescence | 2017
Minh Tan Man; Ji-Hee Kim; Mun Seok Jeong; Anh-Thu Thi Do; Hong Seok Lee
Journal of Raman Spectroscopy | 2012
Kyoung-Duck Park; Yong Hwan Kim; Jin-Ho Park; Jung Su Park; Hong Seok Lee; Sang-Youp Yim; Young Hee Lee; Mun Seok Jeong
Current Applied Physics | 2015
Minh Tan Man; Hong Seok Lee
Current Applied Physics | 2015
Hong Seok Lee; Sanghoon Shin; Heonjoo Lee; Younghun Yu